SGH led a multidisciplinary team, including a stained glass conservator, to investigate issues with the Dalle de Varre panels. We completed field survey and laboratory analysis, including the following:
Optical microscopy and scanning electron microscopy (SEM) to observe the condition of the materials
Chemical analysis using Fourier transform infrared spectroscopy (FTIR) analysis to identify constituents of the mortar matrix and glass adhesive
SGH concluded that the mortar in the transform windows is slowly deteriorating on the outside surface due to ultraviolet (UV) exposure and general weathering. We also determined that the platted glass (multiple glass panes adhered together) is delaminating due to UV degradation of the epoxy-based adhesive and water infiltration could be exacerbating the deterioration.
We recommended the church undertake an immediate protection effort with the assistance of a conservator to remove loose and delaminated glass from the exterior side of the transom panels. We also recommended a topical ultraviolet inhibitor coating to slow the degradation of the mortar matrix.